With the heat wave (30°C/86°F) that everyone here seems to appreciate, heating season 2011/12 is officially over
I summed up some data to see how we did this winter, compared to the previous two seasons for which I have data. As a comparison, I've added our cousin's gas usage (she lives next door). Her usage is much larger than ours since she has a larger house, though it's hard to explain why her gas usage has been going up even though each winter has been slightly warmer than the previous. I'll add that the gas usage includes cooking and hot water (~0.5 m3 per day).
| Oct 1-May 1 | winter 2009-2010 | winter 2010-2011 | winter 2011-2012 |
| HDD (15.5°C) | 2931 | 2848.4 | 2738.5 |
our gas usage
m3 (therms) | 1835 (668) | 1631 (594) | 1401 (510) |
cousin's gas usage
m3 (therms) | 2435 (887) | 2532 (922) | 2594 (945) |
To measure the efficiency of heating between seasons I look at the gas used per HDD.
| Oct 1-May 1 | winter 2009-2010 | winter 2010-2011 | winter 2011-2012 |
our gas usage
efficiency
(m3 per HDD) | 0.63 | 0.57 | 0.51 |
cousin's gas usage
efficiency
(m3 per HDD) | 0.83 | 0.89 | 0.95 |
As you can see, our cousin's heating efficiency over three heating seasons has dropped by almost 15%! I'll have to talk to her about it. On the other hand, I've been able to reduce our gas needs by 20%
I think that's pretty good for a few small mods and aggresive use of the thermostat's controls (among other things: lowering the temperature a bit and seeing how cold it can get when nobody's at home).